A huge amount of US crop land is dedicated to livestock feed. I'm usually skeptical of market based solutions, but an omnivorous diet will probably become a luxury (middle-class people will have a generally herbivorous diet, with occasional meat for special occasions) before factory farming becomes the only way to feed the masses.

Here's a great visualization of how we use our land: https://www.bloomberg.com/graphics/2018-us-land-use/